Magnetic disks, optical disks and magnetic tape cartridges have been all widely used as peripheral digital data storage devices for computer systems. Large computer systems are usually connected with external libraries of multiple such digital data storage devices. Originally, digital data storage devices, such as tape cartridges, were loaded manually. Automated libraries were subsequently developed to expedite the handling of the tape cartridges. Such automated libraries include robotic pickers for accessing, transferring and loading a desired tape cartridge into a reader/writer, and hold the tape cartridges in magazines. Each magazine may hold several tape cartridges in respective slots. Once the library has been up and running, there will be a need to add/remove tape cartridges to/from the library.
In accordance with a prior approach, a magazine is loaded with tape cartridges outside the library, and then the magazine is inserted into the library as a unit and, similarly, removed as a unit. In accordance with another approach, tape cartridges can be inserted individually into the library via a mail-slot.
A further approach is to provide the library with load port specific hardware built into the library. The slots in such load port specific hardware can be configured either as load port slots for adding or removing tape cartridges or as regular storage slots. This arrangement creates a tradeoff between having more load port slots or more storage slots. Also, the built in load ports require different hardware than normal storage slots, because the load port slots need to be accessible by the user while the library is active, and because the load port magazines usually need to be removable. Another problem with built in load ports is that it is difficult to predict how many load port slots a customer may require. In addition, with the built in hardware it is difficult to provide enough flexibility, because the choices of the customer are limited to a range inside the predefined number of configurable load port slots the vendor picks.
Another attempt at making the load port more flexible is to allow each row of slots to be configured as load ports which provides some flexibility in the number of load port slots. Still, this approach causes a trade off between the number of storage slots and the number of load port slots.